Sealing material and method of foaming application thereof

ABSTRACT

Objective problems of the present invention are: to provide a sealing material which does not involve flowing after applied, and shows an excellent sealing performance even under severe heat resistance conditions, and also can make good independent cells inside even when used in a foamed condition; and to provide a method of foaming application of the sealing material. As means of solving these objective problems, the sealing material according to the present invention is characterized by comprising an ultraviolet-curable component and an ultraviolet polymerization initiator and having a thermoplastic elastomer (which is not ultraviolet-curable) content of not higher than 5 weight % and comprising an acrylate as the ultraviolet-curable component and having a melt-viscosity at 120° C. in a certain range wherein the acrylate has a glass transition temperature after ultraviolet curing and a weight-average molecular weight in their respective certain ranges; and the method according to the present invention of foaming application of a sealing material is characterized by comprising the steps of: hot-melting the sealing material; mixing nitrogen gas into the melted sealing material under a predefined pressurization; discharging the resultant mixture at a predefined pressure into the air to thus foam the mixture and simultaneously apply it to a place necessary to seal, thus making a sealing foam; and curing this sealing foam by ultraviolet rays.

TECHNICAL FIELD

The present invention relates to a sealing material and a method offoaming application thereof. In detail, the invention relates to: asealing material which is hot-melting and ultraviolet-curable and isfavorably used particularly as a foamable one; and a method of foamingapplication of the sealing material.

BACKGROUND ART

As known examples of sealing materials, the following examples can becited. However, all of them have the following problems.

Known is a gasket-composite material utilizing a resin compositionobtained by pressure-injecting an inert gas into a compositioncomprising an ethylenically unsaturated compound and a near-infraredphotopolymerization initiator to thus foam the composition into the formof a shake (refer to patent document 1 below). However, since theaforementioned composition is liquid, the composition cannot be leftapplied, so that there is worry that before curing, the compositionmight flow or result in foam breakage.

As a foamed and cured material usable as a foamed gasket material, thereis known a technique in which a predefined foamable polysiloxanecomposition is used and is irradiated with ultraviolet rays at the sametime as being applied, so that the foaming and the curing are caused atthe same time (refer to patent document 2 below). However, if theultraviolet irradiation is not uniform when the aforementionedcomposition is used, then there is a problem that the foam density orfoamed condition is not stable, and further, since the aforementionedcomposition is liquid, the composition cannot be left applied, so thatthere is worry that the composition might flow before curing, and thatas result, the foaming and curing are caused in the flowed condition.

Also known is a photo-reactive sealing material comprising aphoto-reactive composition (refer to patent document 3 below). However,in this technique, similarly to the above-mentioned techniques, sincethe composition is liquid, the composition cannot be left applied, sothat there is worry that the composition might flow before curing.

Also known is a foaming-type sealing composition comprising a rubberyorganic polymer having at least one reactive silicon group, a silanolcondensation catalyst for curing this polymer, and an organic pyrolyzingtype foaming agent (refer to patent document 4 below). However, in thistechnique, similarly to the above-mentioned techniques, since thecomposition is liquid, the composition cannot be left applied, so thatthere is worry that the composition might flow before curing. Inaddition, there must be thermosetting facilities in a line in order tocarry out foaming by utilizing the thermosetting or pyrolyzability, sothat the line constitution is limited.

The above-mentioned techniques are common with each other in respect tohaving the problem of flowing before curing of the composition. Inaddition, these sealing materials having high flowability have a furtherproblem that when being foamed, they involve foam breakage, so thatcells in the inside of the sealing materials become continuous cells,thus resulting in degradation of such as heat resistance, air tightnessand water tightness. As a sealing material which little involves suchproblems of flowing and foam breakage, hot-melt sealing materials areknown.

For example, as a hot-melt sealing material, there is known a lap jointtype pre-sealing material comprising a mixture of such as athermoplastic elastomer, a tackifier resin and a wax (refer to patentdocument 5 below). However, the aforementioned thermoplastic elastomerdoes not have any crosslinked structure, so that when exposed to heatresistance, the sealing material might melt out.

Therefore, there is also known a technique in which in order to make upfor the heat resistance inferiority of the aforementioned hot-melt typesealing material, moisture curing or ultraviolet curing is used togetherwith cooling solidification of the hot-melt type sealing material.

For example, there is known a reactive type hot-melt composition whichcomprises a predefined urethane prepolymer and a predefined copolymerand further comprises a predefined thermoplastic elastomer in order toprevent foaming during the curing (refer to patent document 6 below). Inthis technique, the moisture curing is applied as the aforementionedcuring reaction. However, in this technique, there is worry: during thehot-melting, gelation might occur, or an unreacted component of adiisocyanate compound which is used as a raw material for the urethanepolymer might be discharged into the air, and besides, there is alsoworry that a difference in the adhesive property might be made due tothe difference in temperature or humidity between winter and summer. Inaddition, in cases where the moisture in the air is completely shut downin order to enhance the heating stability, such cases result in the useunder high pressure and are therefore unfavorable in respect to thesafety.

In addition, there is known a ultraviolet-curable hot-melt sealingmaterial which comprises a predefined ultraviolet-curable component, apredefined tackifier resin and a predefined thermoplastic elastomer andis provided with an ultraviolet polymerization initiator (refer topatent document 7 below). According to this technique, the sealingmaterial which is excellent also in heat resistance is assumed to beobtained. However, the heat resistance as referred to therein is on theassumption of a condition of about 80° C. Therefore, if this sealingmaterial is left under severer heat resistance conditions (e.g. notlower than 100° C.) after cured, then the adhesion performance and thecompression-set become worse, so that the degradation of the sealingperformance is unavoidable.

-   [Patent Document 1]-   JP-A-06-192468-   [Patent Document 2]-   JP-A-09-040870-   [Patent Document 3]-   JP-A-2004-269678-   [Patent Document 4]-   JP-A-11-293020-   [Patent Document 5]-   JP-A-01-190781-   [Patent Document 6]-   JP-A-07-062228-   [Patent Document 7]-   JP-A-2006-328382

DISCLOSURE OF THE INVENTION Objective Problems that the Invention is toSolve

Therefore, objective problems that the present invention is to solveare: to provide a sealing material which does not involve flowing afterapplied, and shows an excellent sealing performance even under severeheat resistance conditions, and also can make good independent cellsinside even when used in a foamed condition; and to provide a method offoaming application of the sealing material.

Means of Solving the Objective Problems

The present inventors diligently studied to solve the above objectiveproblems.

In its course, first of all, in order to obtain the sealing materialwhich does not involve flowing, the present inventors directed theirattention to the aforementioned hot-melting and ultraviolet-curablesealing material as disclosed in patent document 7 above. However, theyhave noticed that: in this technique, the thermoplastic elastomer is notultraviolet-curable and therefore its thermoplastic property remainseven after applying of the sealing material, so that the heat resistanceof the sealing material becomes worse. Therefore, they have studiedwhether the amount of the thermoplastic elastomer which is notultraviolet-curable and causes the inferiority of the heat resistancecan be reduced in order to more enhance the heat resistance.

As a result, they have found out that an acrylate having a glasstransition temperature of −70 to 0° C. after ultraviolet curing canprovide a sealing material with softness and a hot-melting property(i.e. a property to melt by heating and to solidify by cooling), so thatthis acrylate having a glass transition temperature of −70 to 0° C.after ultraviolet curing can be used as a substitute component for thethermoplastic elastomer. However, they have also found out that theacrylate having a glass transition temperature of −70 to 0° C. afterultraviolet curing needs to have a weight-average molecular weight of500 to 50,000, and further that the sealing material needs to have amelt-viscosity at 120° C. of 1,000 to 50,000 mPa·s. In addition, theyhave also found out that since the aforementioned acrylate is curable byultraviolet rays, high heat resistance can be ensured, so that theredoes also not occur the problem of the heat resistance degradationcaused in the case of using the thermoplastic elastomer which is notultraviolet-curable. In addition, they have also found out that theaforementioned sealing material also can make good independent cellseven when used for foamable sealing, and therefore, does not only havehigh heat resistance, but also has excellent sealing performance such asair tightness and water tightness.

Furthermore, they have also found out applying conditions favorable forwell forming independent cells when applying the above-mentioned sealingmaterial in a foamed condition.

The present invention has been completed by the above-mentioned findingsand their confirmation.

That is to say, a sealing material according to the present invention ischaracterized by comprising an ultraviolet-curable component and anultraviolet polymerization initiator, wherein in cases where the sealingmaterial further comprises a thermoplastic elastomer which is notultraviolet-curable, its content is not higher than 5 weight % based onthe total amount of the resin components, and wherein the sealingmaterial comprises an acrylate as the ultraviolet-curable component in aratio of not less than 50 weight % based on the total amount of theresin components wherein the acrylate has a weight-average molecularweight of 500 to 50,000 and has a glass transition temperature of −70 to0° C. after ultraviolet curing, and wherein the sealing material has amelt-viscosity at 120° C. of 1,000 to 50,000 mPa·s.

In addition, a method according to the present invention of foamingapplication of a sealing material comprises the steps of: hot-meltingthe sealing material; mixing a pressurized inert gas into the meltedsealing material; discharging the melted sealing material containing thepressurized inert gas into the air to thus foam the sealing material andsimultaneously apply it to a place necessary to seal, thus making asealing foam; and irradiating this sealing foam with ultraviolet rays,thus curing the sealing material; wherein the method is characterized inthat: the mixing of the inert gas is carried out by: using nitrogen gasas the inert gas; pressurizing the nitrogen gas into a pressure of 0.01to 0.1 MPa; and blowing the pressurized nitrogen gas into the sealingmaterial; and the applying of the sealing material is carried out at adischarging pressure of 2.7 to 9.7 MPa.

Effects of the Invention

By using the specific acrylate, the sealing material according to thepresent invention can be provided with the softness and the hot-meltingproperty without using any thermoplastic elastomer which is notultraviolet-curable, and can be prevented from flowing due to fastcooling solidification based on the hot-melting property, and also canbe enhanced in respect to the heat resistance due to the reduction ofthe amount of the aforementioned thermoplastic elastomer which is notultraviolet-curable being used. The aforementioned sealing materialaccording to the present invention can be used both for non-foamablesealing and for foamable sealing, but can make good independent cellsinside while little involving the foam breakage even when used forfoamable sealing, and therefore, does not only have high heatresistance, but also has excellent sealing performance such as airtightness and water tightness. Since the ultraviolet-curable componentcan be cured in a short time, the independent cells can be ensured evenat a comparatively low viscosity.

In addition, since the method according to the present invention offoaming application of a sealing material uses the best applyingconditions when applying the sealing material in a foamed condition,this method can particularly well form independent cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a seal-treated construction exteriorpanel which illustrates an embodiment of the present invention.

FIG. 2 is a sectional view of sealing parts in an applied condition ofthe construction exterior panels.

FIG. 3 is a schematic structural view illustrating a sealing treatmentprocess.

In FIGS. 1 to 3, symbol 10 represents a construction exterior panel,symbols 12 and 14 represent sealing surfaces, symbol 20 represents asealing material, symbol 30 represents a discharging nozzle, and symbol40 represents an ultraviolet lamp.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, detailed descriptions are given about the sealing materialand method of foaming application thereof according to the presentinvention. However, the scope of the present invention is not bound tothese descriptions. And other than the following illustrations can alsobe carried out in the form of appropriate modifications of the followingillustrations within the scope not departing from the spirit of thepresent invention.

[Sealing Material]:

The sealing material according to the present invention cannot only beused for non-foamable sealing, but also can be used for foamablesealing.

It is known that conventional sealing materials are classified intohot-melting (hot-melt type) sealing materials, moisture-curable sealingmaterials, and ultraviolet-curable sealing materials, according todifferences in curing mechanism for curing the sealing material afterhaving formed a sealing matter by applying the sealing material to aplace needing to be sealed. Among these sealing materials, the sealingmaterial according to the present invention is a hot-melting andultraviolet-curable sealing material.

The sealing material according to the present invention is used in amelted condition resultant from hot-melting. The curing, after havingformed the sealing matter by applying (discharging) themelting-conditioned sealing material, is carried out in combination ofboth mechanisms of the cooling solidification and the ultravioletcuring. Usually, the basic shape or structure of the sealing matter isdetermined by cooling, and thereafter the ultraviolet curing proceeds inthe inside of the sealing matter.

The sealing material according to the present invention is usuallyapplied to a sealing treatment in which the sealing foam is formed byfoaming the sealing material during its use.

As is hereinafter specifically described as a composition formulation ofa sealing material suitable for such a curing mechanism or use form, thesealing material according to the present invention comprises anultraviolet-curable component and an ultraviolet polymerizationinitiator, wherein in cases where the sealing material further comprisesa thermoplastic elastomer, its content is not higher than 5 weight %based on the total amount of the resin components, and wherein thesealing material essentially comprises the below-mentioned predefinedacrylate as the aforementioned ultraviolet-curable component.

[Ultraviolet-Curable Component]:

The ultraviolet-curable component is an ultraviolet-curable compound orcomposition which cures due to ultraviolet irradiation. In the sealingmaterial according to the present invention, as this ultraviolet-curablecomponent, there is essentially contained an acrylate having a glasstransition temperature of −70 to 0° C. after ultraviolet curing. As ismentioned below, it is preferable that in the sealing material accordingto the present invention, as an additional ultraviolet-curablecomponent, there is further contained an acrylate having a glasstransition temperature of not lower than 10° C. before ultravioletcuring.

Hereinafter, in the present application specification, for convenience,the acrylate having a glass transition temperature of −70 to 0° C. afterultraviolet curing might be expressed as “low-Tg acrylate”, and theacrylate having a glass transition temperature of not lower than 10° C.before ultraviolet curing might be expressed as “high-Tg acrylate”.

Hereupon, the “acrylate” in the present invention is a conception whichis not limited to monoacrylates, but also include polyfunctionalacrylates. Therefore, the “acrylate” in the present invention can besaid to be that which contains one or more acryloyl groups per molecule.If the “acrylate” in the present invention is irradiated withultraviolet rays, then the aforementioned acryloyl group acts as areaction site to thus make a crosslinked structure. Therefore, as thenumber of the acryloyl groups becomes larger, the crosslinking becomescloser, so that the sealing material becomes more excellent in the heatresistance. However, if the number of the acryloyl groups is too large,then the softness decreases. From such a viewpoint, the number of theacryloyl groups per molecule is favorably in the range of 2 to 5.

As to the low-Tg acrylate, the use of at least one kind is enough, butthe use of two or more kinds is also not hindered. Also in cases wherethe high-Tg acrylate is used together with the low-Tg acrylate, suchcases are not limited to the use of one kind of high-Tg acrylate, buttwo or more kinds of high-Tg acrylates may be used together with thelow-Tg acrylate. Furthermore, one kind or two or more kinds of acrylatesother than the high-Tg acrylate and the low-Tg acrylate may be usedtogether with the low-Tg acrylate.

The weight-average molecular weight of the low-Tg acrylate according tothe present invention needs to be in the range of 500 to 50,000 and ispreferably in the range of 500 to 30,000. In addition, also as to theacrylate such as high-Tg acrylate other than the low-Tg acrylate, theweight-average molecular weight is preferably in the range of 500 to50,000 and is more preferably in the range of 500 to 30,000. If themolecular weight is too large, then the viscosity might become high, sothat the application performance might become inferior. If the molecularweight is too small, then the viscosity might become low, so that theflowing might easily occur and, in cases where the sealing material isused for foamable sealing, the foam breakage might easily occur and agood independent-cell matter might become difficult to obtain.

The low-Tg acrylate has a glass transition temperature of −70 to 0° C.after ultraviolet curing. If the glass transition temperature afterultraviolet curing is higher than 0° C., it might be impossible toprovide enough softness, so that the compression-set might be lower. Ifthe glass transition temperature after ultraviolet curing is lower than−70° C., the viscosity might become too low, so that the flowing mightoccur and further, also in cases where the sealing material is used forfoamable sealing, the foam breakage might easily occur and a goodindependent-cell matter might become difficult to obtain. The glasstransition temperature after ultraviolet curing is preferably in therange of −50 to 0° C.

The low-Tg acrylate is not especially limited. However, examples thereofinclude: those which are obtained by introducing an acryloyl group intoa molecule by utilizing isocyanate groups of an urethane prepolymerobtained by a reaction between a low-Tg polyester-polyol orpolyether-polyol and an isocyanate; those which are obtained byintroducing an acryloyl group into a molecule by utilizing an oxiranering of an epoxy resin; and those which are obtained by grafting anacryloyl group onto a side chain of a copolymer of comonomers one ofwhich is n-butyl acrylate (n-BA).

The high-Tg acrylate which is favorably used together with the low-Tgacrylate as the ultraviolet-curable components has a glass transitiontemperature of not lower than 10° C. before ultraviolet curing. By usingthe aforementioned high-Tg acrylate together with the low-Tg acrylate,the melt viscosity at 120° C. of the sealing material can be increased,so that the flowing can remarkably be prevented and also that even incases where the sealing material is used for foamable sealing, the foambreakage can be prevented so remarkably as to easily obtain goodindependent cells and also the tackiness of the sealing material can beenhanced. If the aforementioned glass transition temperature is lowerthan 10° C., then it might become impossible to provide theaforementioned effects enough. On the other hand, if the aforementionedglass transition temperature is too high, then the viscosity mightbecome so high as to cause problems that the application performance isdegraded or that the heating temperature needed for the hot-meltingbecomes high. Therefore, the aforementioned glass transition temperatureis favorably not higher than 100° C. and more favorably in the range of20 to 80° C.

The high-Tg acrylate is not especially limited. However, examplesthereof include: oligomers obtained by grafting an acryloyl group onto aside chain of a copolymer of comonomers one of which is methylmethacrylate (MMA); those which are obtained by introducing an acryloylgroup into a side chain of a rosin ester; those which are obtained bygrafting an acryloyl group by utilizing a phenolic hydroxyl group of aterpene phenol resin; and those which are obtained by introducing anacryloyl group by utilizing a residue of a non-reactive tackifier resin.

In cases where the high-Tg acrylate is used together with the low-Tgacrylate, the ratio between the low-Tg acrylate and the high-Tg acrylatedepends on their respective glass transition temperatures, but is, forexample, favorably in the range of 90:10 to 60:40 and more favorably inthe range of 80:20 to 70:30.

The ultraviolet-curable component may include known otherultraviolet-curable compounds besides the above specific acrylates.

The above other ultraviolet-curable compounds are not especiallylimited. However, for example, the below-explained cationicpolymerization type ultraviolet-curable compounds are favorably used.

As the cationic polymerization type ultraviolet-curable compounds,epoxidized compounds of known or commercially available various kinds ofliquid polydienes can be used. Specific examples thereof include: thosewhich are obtained by setting-in an epoxy group into such as polydienecompounds having a 1,2-polybutadiene conformation synthesized by anionicliving polymerization technique or their hydrogenated products; thosewhich are obtained by setting-in an epoxy group into polydiene compoundsproduced by radical polymerization; and those which are obtained bysetting-in an epoxy group into molecules of liquid polydiene typeoligomers by reactions between a terminal end group of the liquidpolydiene type oligomers and an epoxy group of such as epoxy resins.Herein, the epoxy resins are those which have two or more epoxy groupsper molecule.

Examples of commercially available products of the ultraviolet-curablecompounds having an epoxy group include: trade name “R-45EPT” producedby Nagase ChemteX Corporation; trade name “PB-3600” produced by DaicelChemical Industries, Ltd.; and trade name “L-207” produced by CratonPerformance Polymers, Inc.

The weight-average molecular weight of the ultraviolet-curable compoundhaving an epoxy group is not especially limited. However, it is in therange of 100 to 50,000, favorably 100 to 30,000, more favorably 100 to20,000. If the molecular weight is too high, then the operation propertyis inferior, so that the application property of the sealing material isnot good. If the molecular weight is too low, then enough softness isnot obtained, so that the sealing performance is degraded.

[Ultraviolet-Curable Components as Composition]:

The ultraviolet-curable component may only comprise the aforementionedultraviolet-curable compounds, but may be a composition obtained bytaking these compounds in combination with such as epoxy resins.

Examples of the aforementioned epoxy resins include the following ones.

<Epoxy Resins>:

Those which have two or more epoxy groups per molecule are used.

Glycidyl type epoxy resins can be used. Specific examples thereofinclude: bisphenol A types; bisphenol F types; bisphenol S types; flameretardant types of tetrabromobisphenol A; phenol novolac types; cresolnovolac types; hydrogenated bisphenol A types; and propylene oxide orethylene oxide adducts of bisphenol A types.

Glycidyl ester type epoxy resins can be used. Specific examples thereofinclude: diglycidyl ester of hexahydrophthalic acid; and diglycidylesters of dimer acids.

Glycidyl amine type epoxy resins can be used. Specific examples thereofinclude: triglycidyl isocyanate; andtetraglycidyldiaminodiphenylmethane.

Linear aliphatic epoxy resins can be used. Specific examples thereofinclude: epoxidized polybutadiene; and epoxidized soy bean oil.

Alicyclic epoxy resins can be used. Specific examples thereof include:alicyclic diepoxyacetals; alicyclic diepoxyadipates; alicyclicdiepoxycarboxylates; and vinylcyclohexene oxide.

[Ultraviolet Polymerization Initiator]:

In the present invention, when the ultraviolet-curable component iscured, the ultraviolet polymerization initiator is used.

When the aforementioned acrylate as an ultraviolet-curable component iscured, a radical ultraviolet polymerization initiator is used.

As the radical ultraviolet polymerization initiator, known ones can beused adequately. However, specific examples thereof include: benzoinssuch as benzoin, benzoin methyl ether and benzoin ethyl ether, and theiralkyl ethers; acetophenones such as acetophenone,2,2-dimethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone and4-(1-t-butyldioxy-1-methylethyl)acetophenone; anthraquinones such as2-methylanthraquinone, 2-amylanthraquinone, 2-t-butylanthraquinone and1-chloroanthraquinone; thioxanthones such as 2,4-dimethylthioxanthone,2,4-diisopropylthioxanthone and 2-chlorothioxanthone; ketals such asacetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenonessuch as benzophenone, 4-(1-t-butyldioxy-1-methyl ethyl)benzophenone, and3,3′,4,4′-tetrakis(t-butyldioxycarbonyl)benzophenone;2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1;acylphosphine oxides and xanthones.

Examples of commercially available products of the radicalpolymerization initiator include trade name “Irgacure 184” produced byCiba-Geigy AG.

In addition, in the aforementioned case where other ultraviolet-curablecompounds are also used as the ultraviolet-curable components,corresponding polymerization initiators are properly used. For example,in cases where the aforementioned cationic polymerization typeultraviolet-curable compounds are contained, cationic ultravioletpolymerization initiators are properly used.

Appropriate cationic ultraviolet polymerization initiators are properlyselected and used according to the materials or composition formulationsused for the cationic polymerization type ultraviolet-curable compounds.

As the cationic ultraviolet polymerization initiators, for example,onium salts can be used. The onium salts are organic salts comprisingonium ions and anions and generate Lewis acids and Brφnsted acids(protonic acid) by ultraviolet irradiation.

Specific examples of the onium salts include diphenyl iodonium,4-methoxydiphenyl iodonium, bis(4-methylphenyl) iodonium,bis(4-tert-butylphenyl) iodonium, bis(dodecylphenyl) iodonium, tricummyliodonium, triphenyl sulfonium, bis(4-(diphenylsulfonio)-phenyl) sulfide,bis(4-(di(4-(2-hydroxyethyl)phenyl)sulfonio)-phenyl) sulfide, andη5-2,4-(cyclopentadienyl)(1,2,3,4,5,6-η-(methylethyl)benzene)-iron (1+).

Specific examples of the anions include tetrafluoroborate,tetrakis(pentafluorophenyl)borate, hexafluorophosphate,hexafluoroantimonate, hexafluoroarsenate and hexachloroantimonate.

Examples of commercially available products of the cationicpolymerization initiator include trade name “Adekaoptomer SP-150”produced by ADEKA Co., Ltd.

[Sensitizer]:

In order to enhance the ultraviolet curability, a sensitizer may beused. Specific examples of the sensitizer include: unsaturated ketonesrepresented by such as chalcone derivatives and dibenzalacetone;1,2-diketone derivatives represented by such as benzyl andcamphorquinone; benzoin derivatives; fluorene derivatives;naphthoquinone derivatives; anthraquinone derivatives; xanthenederivatives; thioxanthene derivatives; xanthone derivatives;thioxanthone derivatives; coumarin derivatives; ketocoumarinderivatives; cyanine derivatives; merocyanine derivatives; polymethinedyes such as oxonol derivatives; acridine derivatives; azinederivatives; thiazine derivatives; oxazine derivatives; indolinederivatives; azulene derivatives; azulenium derivatives; squaliriumderivatives; porphyrin derivatives; tetraphenylporphyrin derivatives;triarylmethane derivatives; tetrabenzoporphyrin derivatives;tetrapyrazinoporphyrazine derivatives; phthalocyanine derivatives;tetraazaporphyrazine derivatives; tetraquinoxaliroporphyrazinederivatives; naphthalocyanine derivatives; subphthalocyaninederivatives; pyrylium derivatives; thiopyrylium derivatives; tetraphyrinderivatives; annulene derivatives; spiropyran derivatives; spirooxazinederivatives; thiospiropyran derivatives; metal arene complexes; andorganoruthenium complexes.

[Tackifier Resin]:

In order to adjust the hot-melting property of the sealing material,various kinds of tackifier resins which are utilized for conventionalhot-melt type sealing materials can be added. However, in the sealingmaterial according to the present invention, the tackiness can beprovided to the sealing material by adding thereto the above-mentionedlow-Tg acrylate, and particularly, the aforementioned tackiness also canfurther be enhanced by using the high-Tg acrylate together with thelow-Tg acrylate. Therefore, even if the below-explained tackifier resinsare not used, that will do.

Various kinds of tackifier resins which are utilized for conventionalsealing materials, particularly, hot-melt type sealing materials, can beused.

Specific examples of the tackifier resins include: rosins, modified(e.g. hydrogenated) rosins, and rosin derivatives which are theiresterified products; terpene type resins which are polymers of terpenessuch as α-/β-pinene and dipentene; modified terpene resins such asterpene phenol resins; coumarone indene resins; and various kinds ofaliphatic, alicyclic and aromatic hydrocarbon resins, and theirhydrogenated resins.

[Thermoplastic Elastomer]:

Similarly to the tackifier resin, various kinds of thermoplasticelastomers which are utilized for conventional hot-melt type sealingmaterials can be used. However, in the sealing material according to thepresent invention, the hot-melting property and the softness can beprovided by the low-Tg acrylate, and particularly, the aforementionedhot-melting property also can further be enhanced by using the high-Tgacrylate together with the low-Tg acrylate. Therefore, even if thebelow-explained thermoplastic elastomers are not used, that will do.

The aforementioned thermoplastic elastomer is not especially limited.However, for example, thermoplastic block copolymers having two or moreof polystyrene blocks and one or more of elastic polymer blocks can beused. Specific examples include styrene-butadiene block copolymers (SBS)and their hydrogenated products (SEBS), and styrene-isoprene blockcopolymers (SIS). Thermoplastic elastomers obtained by grafting an epoxygroup or carboxyl group onto the above elastomers can also be used.

[Waxes]:

Various kinds of waxes which are utilized for conventional hot-melt typesealing materials can be added.

Specific examples include the following natural waxes: paraffinscomprising a major proportion of n-paraffins or iso-paraffins ascontained in crude petroleum residue during petroleum purification;microcrystalline wax; montan wax produced from montanic acid which is anextract from coal; carnauba wax obtained from Copernica cerifera Mart;and candelilla wax obtained from grass stalks. In addition, examples ofsynthetic waxes include polyethylene wax produced from ethylene.

Examples of waxes preferably used of the above ones include paraffins,microcrystalline, Fischer-Tropsch, various kinds of low-molecularpolyethylene waxes, some of modified waxes, and atactic polypropylene.

The natural waxes have a molecular weight of 300 to 800, so that theirmelting points are also low. As to the synthetic waxes, thepolymerization degree can freely be changed, so that the melting pointbecomes higher by the difference in molecular weight. Generally, many ofthe synthetic waxes have a molecular weight in the range of about 1,000to about 10,000.

[Composition Formulation and Properties of Sealing Material]:

In order to prepare the sealing material, the above-mentioned componentmaterials are mixed together in their respective proper amounts.However, in view of the heat resistance, the ultraviolet-curablecomponent is contained favorably in a major proportion, specifically, ina ratio of not less than 90 weight % based on the total amount of theresin components.

The low-Tg acrylate which is essentially used as an ultraviolet-curablecomponent needs to be contained in a ratio of not less than 50 weight %based on the total amount of the resin components. If the ratio of thelow-Tg acrylate is less than 50 weight %, then the low-Tg acrylatecannot sufficiently be substituted for the performances (e.g. hot-meltproperty, softness) of the thermoplastic elastomer.

In cases where the thermoplastic elastomer which is notultraviolet-curable is also used, this component has a great influenceon the degradation of the heat resistance, so that the amount of thethermoplastic elastomer which is not ultraviolet-curable needs to be nothigher than 5 weight % based on the total amount of the resincomponents.

Similarly, in view of the heat resistance, in cases where the tackifierresin which is not ultraviolet-curable is also used, its amount isfavorably not higher than 5 weight % based on the total amount of theresin components, and also in cases where the wax is also used, itsamount is favorably not higher than 5 weight % based on the total amountof the resin components. Also as to these components, if theirrespective amounts are too large, then the heat resistance degradationmight be caused.

The ultraviolet polymerization initiator is contained, for example, inan amount of 0.1 to 10 weight % based on the ultraviolet-curablecomponent.

As to the properties of the hot-melt type sealing material, for example,the hot-melting temperature can be set in the range of 30 to 130° C. Themelt-viscosity at 120° C. needs to be in the range of 1,000 to 50,000mPa·s. If the melt-viscosity at 120° C. is in the aforementioned range,then the flowing does not occur, and even in cases where the sealingmaterial is used for foamable sealing, the foam breakage does not occur,so that good independent cells can be produced. The melt-viscosity at120° C. is favorably in the range of 1,000 to 30,000 mPa·s and morefavorably in the range of 1,000 to 20,000 mPa·s. The melt-viscosity at120° C. can easily be set in the aforementioned ranges by properlydetermining such as glass transition temperature or weight-averagemolecular weight of the acrylate and the content of the tackifier resinor thermoplastic elastomer.

[Various Kinds of Additives]:

The sealing material according to the present invention can be usedfurther with additives added thereto according to such as purpose of theuse of the sealing material, wherein the additives are, for example, asfollows: dyes; organic and inorganic pigments; deoxidants or reductantssuch as phosphines, phosphonates and phosphites; seam inhibitors;discoloring inhibitors; halation inhibitors; fluorescent brighteningagents; surfactants; colorants; fillers; plasticizers; flame retardants;antioxidants; ultraviolet absorbents; antimolds; antistatic agents;magnetic matters; and other additives for providing various properties.In addition, the sealing material also can be used with such as dilutingsolvents mixed therewith.

[Uses of Sealing Material]:

Basically, techniques common with conventional hot-melt type sealingmaterials and ultraviolet-curing type sealing materials can be applied.

Usually, the sealing material is supplied to a member for providing thesealing performance or to a place needing to be sealed of apparatus anddevices, for example, to a sealing surface, thereby forming a sealingmatter on the sealing surface, and then the sealing matter as placed onthe sealing surface contacts with a sealing surface of another member,so that the sealing performance is performed.

Specifically, an application method comprising the following steps canbe adopted. Hereinafter, particularly a foaming application method forapplying the sealing material in a foamed condition is explained indetail. However, in cases where the application without foaming thesealing material is desired, it is enough that in the following, theblowing-in of the inert gas is not carried out.

<Step (a): Hot-Melting and Blowing-in of Inert Gas>:

A pressurized inert gas is blown into a hot-melted sealing material.This is a step which is also applied to conventional hot-melt typesealing materials, so that the same treatment devices and conditions canbe applied.

The sealing material is usually solid at normal temperature and istherefore beforehand hot-melted in order to have a liquidity.Specifically, when the sealing material is hot-melted, the heatingtemperature of the sealing material can be set in the range of 30 to130° C.

In order to form a sealing foam, the pressurized inert gas is blown intothe melted sealing material. As the inert gas, such as nitrogen gas orcarbon dioxide can be used. The gas is favorably fed in a conditionpressurized into a pressure of 0.01 to 0.1 MPa (gas cylinder pressure).If the gas cylinder pressure is too low, then it might be impossible toobtain enough foamability. If the gas cylinder pressure is too high,then it is difficult to obtain uniform independent cells.

The hot-melting of the sealing material and the blowing-in of the inertgas are usually carried out before the below-mentioned discharging ofthe sealing material. However, the blowing-in of the inert gas also canbe carried out just before or at the same time as the discharging of thesealing material. The sealing material also can be discharged while theinert gas is blown into the sealing material. The sealing material alsocan be discharged by the pressurizing force due to the blowing-in of theinert gas.

This step (a) and the next step (b) may be carried out as separatesteps, or there is a case where these steps are carried out as the samestep or carried out simultaneously or continuously with the sameapparatus.

<Step (b): Discharging and Foaming>:

The melted sealing material containing the pressurized inert gas isdischarged into the air to thus foam the sealing material andsimultaneously apply it to a place necessary to seal, thus making asealing foam. This is the same operation as that for conventionalhot-melt type sealing materials, so that the same treatment devices andconditions can be applied.

The discharging pressure is not especially limited. However, thedischarging pressure is favorably in the range of 2.7 to 9.7 MPa. If thedischarging pressure is too low, then the foam density might be low, sothat the resultant foam might lack elasticity and therefore have a lowsealing property, and further that occasionally, a stress more thannecessary might unfavorably be applied to a place to be sealed. On theother hand, the discharging pressure is too high, then the foam breakagemight be caused, so that it might be impossible to obtain anyindependent cell.

The melted sealing material as discharged into the air resides on asealing surface in the form of a block having a predefined thickness orsectional shape and is solidified by cooling. On this occasion, thepressurized inert gas expands to cause a foaming phenomenon which formsfine cells or hollows in the inside of the sealing material.

The foam density of the sealing foam as obtained by foaming the sealingmaterial is favorably set in the range of 2 to 4 densities. The foamdensity makes differences in respect to the softness, elasticity andsealing performance of the finally obtained sealing foam. If the foamdensity is too low, then enough deformability cannot be provided. If thefoam density is too high, then the deformability is too much, so thatenough sealing performance cannot be performed.

If the sealing material has been cool-solidified by leaving the sealingfoam, then the same sealing foam as conventional hot-melt type sealingmaterial is formed. However, in the present invention, as mentionedbelow, furthermore, an ultraviolet irradiation treatment is carried out.

If, while a member having a sealing surface is continuously run, thesealing material is discharged in a fixed position, then a continuousmaterial of the discharged sealing material, that is, a sealing foam, isformed on the sealing surface. The sectional area and shape of thesealing foam being formed can be adjusted by adjusting the running speedof the sealing surface and the shape and discharging amount of thenozzle for discharging the sealing material.

<Step (c): Ultraviolet Curing>:

The sealing material as applied to the sealing surface while beingfoamed in the aforementioned step (b), that is, the sealing foam, isimmediately irradiated with ultraviolet rays and thereby cured.

As to the discharged foaming of the sealing material and the ultravioletirradiation thereto, there is a case where they are substantiallysimultaneously started. Or the ultraviolet irradiation also can becarried out after the discharging and foaming of the sealing materialhave been carried out enough.

To the ultraviolet irradiation, basically, there can be applied the sameapparatus and treatment conditions as those for ultraviolet curingtreatment to conventional ultraviolet-curable compositions.

As ultraviolet rays to be irradiated, ultraviolet rays having awavelength of 200 to 400 nm can be irradiated at an irradiationintensity of 1 to 10,000 mW/cm².

While the sealing surface on which the sealing foam has been formed iscontinuously run, ultraviolet rays can be irradiated by an ultravioletirradiation means as set with fixation. The irradiation dose per unittime and the irradiation time can be adjusted by adjusting the runningspeed of the sealing surface and the intensity of the ultraviolet rays.

Of course, it is also possible that an ultraviolet irradiation lamp orultraviolet beam is moved in a condition where the sealing foam remainsfixed.

[Uses of Sealing Material]:

The ultraviolet-curable hot-melt type sealing material and the foamingapplication method, according to the present invention, can be appliedto the same uses as those of conventional hot-melt type sealingmaterials and ultraviolet-curable type sealing materials. Particularly,when used under severe environments such as outdoor, the sealingmaterial according to the present invention can show excellentperformance. Even under environments which cannot avoid the contact withwater such as water wetting and under environments which are put in ahigh-temperature condition much exceeding normal temperature, thesealing material according to the present invention shows excellentsealing performance.

Specifically, examples of uses of the sealing material according to thepresent invention include the following:

for automobile parts, for example, housing seals for lamps such asheadlamps, door modules, and interior seals;

construction materials, for example, seal parts of exterior panelsconstituting exterior walls, seal parts of roof materials, and lap jointparts of such as metal sizing materials; and

household appliances, for example, seal places of such as refrigerators,air conditioners and washing machines.

[Form of Use of Sealing Material]:

FIGS. 1 and 2 show a case where a sealing material has been applied tosealing parts of construction exterior panels to be applied onto such asexterior walls of constructions.

As is shown in FIG. 1, the construction exterior panel 10 comprisingsuch as light-weight concrete panels has, in face-to-face side edgeparts, bump-shaped notches to be joint parts for connection, and thesurfaces of the bump parts are to be the sealing surfaces 12 and 14.Since the bump shapes are reverse in front and back relations at theface-to-face side edges, the sealing surface 12 and the sealing surface14 are reverse in front and back relations. Such a connection structurein which the sealing surfaces 12 and 14 face with each other might becalled lap joint.

The bead-shaped sealing foam 20 continuous along the longitudinaldirection is applied onto the sealing surface 12 exposed to the frontside of the construction exterior panel 10. The sealing foam 20 has anapproximately semicircular sectional shape.

As is shown in FIG. 2, the construction exterior panels 10 are appliedonto the construction substrate material 16 by sticking. Theconstruction exterior panels 10 are applied from side to side insequence. Onto the sealing surface 12 of the construction exterior panel10, there is face-to-face placed the back-oriented sealing surface 14 ofthe construction exterior panel 10 being adjacently applied. The sealingsurface 14 contacts with the sealing foam 20 and presses it downward.The sealing foam 20 softly deforms and thereby adheres to the sealingsurface 14, so that the sealing performance is shown.

In the case of the construction exterior panels 10, they are exposed tothe outdoor environment for a long time. Factors such as sunlight,difference between day warmness and night coldness, and rain giveinfluence on the sealing foam 20 exposed to gaps between the connectionparts of the construction exterior panels 10. Therefore, the sealingfoam 20 is required to have such as heat resistance, water resistanceand temperature change resistance to outdoor environment.

The above-mentioned application of the sealing foam 20 onto theconstruction exterior panels 10 also can be carried out in applicationfields of constructions, but it is effective that the application isbeforehand carried out in such as production factories for theconstruction exterior panels 10.

[Application of Sealing Material]:

FIG. 3 shows a applied condition of the sealing foam 20 in such asproduction factories for the construction exterior panels 10.

The construction exterior panel 10 is continuously run using such asconveyor apparatus in a condition where the sealing surface 12 is setupward. Though drawing is omitted, on the upstream side of the runningcourse, there may be set a producing step or processing step for theconstruction exterior panels 10. Also on the downstream side of therunning course, there may be set another processing step of treatingstep for the construction exterior panels 10. Shown in FIG. 3 is acondition where the sealing treatment step is incorporated on the way ofthe production line for the construction exterior panels 10.

In the running course of the construction exterior panels 10, there isset the nozzle 30 for discharging the sealing material 22. Thedischarging nozzle 30 is a part of an applicator apparatus, of which thedrawing has been omitted, and is connected with a reservoir tank for thesealing material 22, wherein the tank is provided to the applicatorapparatus. The sealing material 22 is heated by such as heater into amelted condition in the reservoir tank or in the course of from thereservoir tank to the discharging nozzle 30. Pressurized nitrogen gas isblown into the melting-conditioned sealing material 22. Specifically,the sealing material 22 can be heated to 120° C., and thereinto,nitrogen gas can be blown at a pressure of 29 kPa.

As a specific example of such an apparatus for discharge-supplying thesealing material 22, Foam Melt Applicator FM-151 Model (trade name,produced by Nordson Corporation) can be used. In this applicator,nitrogen gas is blown into the hot-melted sealing material 22mechanically with a particular gear pump and discharged into the air andthereby foamed.

The melted sealing material 22 as discharged onto the sealing surface 12of the running construction exterior panel 10 results in forming acontinuous bead on the sealing surface 12. For example, the runningspeed of the sealing surface 12 can be set for 15 m/min.

When discharged from the discharging nozzle 30, the sealing material 22being put under normal pressure is foamed by expansion of thepressurized nitrogen gas, so that independent cells are formed in theinside of the sealing material 22. In addition, since the heated sealingmaterial 22 rapidly cools and solidifies, the aforementioned bead shaperemains kept, so that the sealing material 22 does not extend over awide range of the sealing surface 12 in the form of a liquid. Thefoaming phenomenon can promote the cooling and thereby can rapidlysolidify the sealing material 22 in a proper bead shape.

Just on the downstream side of the discharging nozzle 30 in the runningcourse of the construction exterior panels 10, there is placed theultraviolet irradiation lamp 40. The ultraviolet irradiation lamp 40 isirradiated to the sealing foam 20 formed from the sealing material 22.The ultraviolet curing occurs in the inside of the sealing foam 20. Theconditions of the ultraviolet irradiation, for example, can be set sothat ultraviolet rays having a wavelength of 200 to 400 nm areirradiated at an irradiation intensity of 2,000 mW/cm² to expose eachpart of the running sealing foam 20 to the ultraviolet rays for 30seconds.

As a specific example of such an ultraviolet irradiation system, tradename “Light Hammer 6” produced by Fusion UV Systems, Japan, K.K. can beused.

Since the sealing material 22 contains the ultraviolet-curable componentand the ultraviolet polymerization initiator, the curing rapidlyproceeds due to the ultraviolet irradiation. Each part of the sealingmaterial 22 only passes the irradiation region of the ultravioletirradiation lamp 40 in a short time, but sufficiently undergoes theaction of the ultraviolet rays, so that the ultraviolet curing israpidly started, and further that the ultraviolet curing rapidlyproceeds from the surface to inside of the sealing foam 20 and, as aresult, the ultraviolet curing rapidly proceeds throughout the entiretyof the sealing foam 20 having some degree of thickness.

The construction exterior panels 10 having passed the position of theultraviolet irradiation lamp 30 also can be fed out to the nexttreatment step or subjected to a shipping or safekeeping work. Thesealing foam 20 on the sealing surface 12 has enough shaperetainability, and its surface does not have strong stickiness, and evenif the surface is subject to the touch or to the contact with anotherobject, the shape is not deformed, or damage is not done.

WORKING EXAMPLES

Hereinafter, the present invention is more specifically illustrated bythe following Examples of some preferred embodiments in comparison withComparative Examples not according to the present invention. However,the present invention is not limited to these examples.

Examples 1 to 7 Comparative Examples 1 to 3

The ultraviolet-curable component and the ultraviolet polymerizationinitiator and further, optionally, the thermoplastic elastomer and thetackifier resin according to the composition formulations as shown inTable 1 below were stirred and mix-kneaded together to thereby preparesealing materials of Examples 1 to 7 and Comparative Examples 1 to 3,and these sealing materials were measured for the melt-viscosity at 120°C. The results are shown in Table 1. Incidentally, the numerical valuesas to the formulations in Table 1 represent weight parts.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Ultraviolet-curable High-Tg acrylate A 25 40 10 5 component High-Tgacrylate B 25 40 Low-Tg acrylate C 50 50 50 50 55 50 Low-Tg acrylate D25 10 25 10 25 20 Low-Tg acrylate E Cationic-polymerizable compound F 10Cationic-polymerizable compound G 10 Ultraviolet polymerization Radicalpolymerization initiator 3 3 3 3 3 3 initiator Cationic polymerizationinitiator 1 Tackifier resin 5 Thermoplastic elastomer 5 Melt-viscositymPa · s/120° C. 5000 6000 8800 10000 6000 6000 Comparative ComparativeComparative Example 7 Example 1 Example 2 Example 3 Ultraviolet-curableHigh-Tg acrylate A component High-Tg acrylate B Low-Tg acrylate C 70 7550 Low-Tg acrylate D 25 25 Low-Tg acrylate E 100 Cationic-polymerizablecompound F Cationic-polymerizable compound G Ultraviolet polymerizationRadical polymerization initiator 3 3 3 3 initiator Cationicpolymerization initiator Tackifier resin 20 Thermoplastic elastomer 10Melt-viscosity mPa · s/120° C. 1200 4000 800 900 High-Tg acrylate A:IBA-100 (produced by Soken Chemical & Engineering Co., Ltd.; Mw: 10,000,Tg before ultraviolet curing: 20° C.) High-Tg acrylate B: Beamset 101(produced by Arakawa Chemical Industries, Ltd.; Mw: 430, Tg beforeultraviolet curing: 18° C.) Low-Tg acrylate C: Shikoh-UV-3000B (producedby Nippon Synthetic Chemical Industry Co., Ltd.; Mw: 18,000, Tg afterultraviolet curing: −52° C.) Low-Tg acrylate D: Shikoh-UV-3700B(produced by Nippon Synthetic Chemical Industry Co., Ltd.; Mw: 38,000,Tg after ultraviolet curing: −59° C.) Low-Tg acrylate E: Shikoh-UV-2000B(produced by Nippon Synthetic Chemical Industry Co., Ltd.; Mw: 13,000,Tg after ultraviolet curing: −40° C.) Cationic-polymerizable compound F:Epicoat 828 (produced by Japan Epoxy Resin Co., Ltd., Mw: 380)Cationic-polymerizable compound G: PB-3600 (produced by Daicel ChemicalIndustries, Ltd.) Radical polymerization initiator: Irgacure 184(produced by Ciba Speciality Chemicals Co., Ltd., 1-hydroxycyclohexylphenyl ketone) Cationic polymerization initiator: Cyracure CPI-6992 (TheDow Chemical Company: sulfonium salt) Tackifier resin: terpene phenoltype resin, softening point: 120° C. Thermoplastic elastomer: VylonGA-6400 (produced by Toyobo Co., Ltd.: saturated polyester resin)

The melt-viscosity as shown in Table 1 was measured under the followingconditions.

<Melt-Viscosity>:

The sealing materials of Examples 1 to 7 and Comparative Examples 1 to 3were measured for the melt-viscosity (mPa·s) at 120° C. with aBrookfield type Themosel System viscometer, #27 spindle by aconventional method.

Next, the foam density, the flowing, the UV reactivity, theheat-resistant blocking, the compression-set, the hardness, the watertightness and the foamability were evaluated.

In these evaluations, first of all, as condition 1, each of the abovesealing materials of Examples 1 to 7 and Comparative Examples 1 to 3 washot-melted, foamed and discharged under the following condition, andthen each evaluation was carried out. The results are shown in Table 2.

(Condition 1):

Each of the above sealing materials of Examples 1 to 7 and ComparativeExamples 1 to 3 was hot-melted at a temperature of 120° C. with FoamMelt Applicator (trade name “FM-151”, produced by Nordson Corporation),and then nitrogen gas was mixed into the melting-conditioned sealingmaterial at a gas cylinder pressure of 0.05 MPa, and then themelting-conditioned sealing material containing the pressurized nitrogengas was discharged into the air at a discharging pressure of 5.0 MPa andthereby foamed.

TABLE 2 (Condition 1) Example 1 Example 2 Example 3 Example 4 Example 5Example 6 Ultraviolet-curable High-Tg acrylate A 25 40 10  5 componentHigh-Tg acrylate B 25 40 Low-Tg acrylate C 50 50 50 50 55 50 Low-Tgacrylate D 25 10 25 10 25 20 Low-Tg acrylate E Cationic-polymerizablecompound F 10 Cationic-polymerizable compound G 10 Ultravioletpolymerization Radical polymerization initiator  3  3 3  3  3  3initiator Cationic polymerization initiator  1 Tackifier resin  5Thermoplastic elastomer  5 Foam density densities  3  3 3  3  3  3Flowing ◯ ◯ ◯ ◯ ◯ ◯ UV reactivity Sticky or not No No No No No NoIrradiation intensity: 2000 mW/cm² Irradiation time: 30 secondsHeat-resistant blocking 100° C./after 5 days ◯ ◯ ◯ ◯ ◯ ◯ Compression-set80° C. × 24 hours (50% compression) ◯ ◯ ◯ ◯ ◯ ◯ and thereafter releasingat 23° C. Hardness 23° C. (Shore 00) 45 45 45 46 48 50 Water tightness23° C. × 24 hours ◯ ◯ ◯ ◯ ◯ ◯ (during 50% compression) FoamabilityContinuous or independent ◯ ◯ ◯ ◯ ◯ ◯ Comparative ComparativeComparative Example 7 Example 1 Example 2 Example 3 Ultraviolet-curableHigh-Tg acrylate A component High-Tg acrylate B Low-Tg acrylate C 70 7550 Low-Tg acrylate D 25 25 Low-Tg acrylate E 100  Cationic-polymerizablecompound F Cationic-polymerizable compound G Ultraviolet polymerizationRadical polymerization initiator 3  3  3  3 initiator Cationicpolymerization initiator Tackifier resin 20 Thermoplastic elastomer 10Foam density densities 3  3  3  3 Flowing ◯ ◯ X X UV reactivity Stickyor not No Yes No No Irradiation intensity: 2000 mW/cm² Irradiation time:30 seconds Heat-resistant blocking 100° C./after 5 days ◯ X ◯ ◯Compression-set 80° C. × 24 hours (50% compression) ◯ ◯ ◯ ◯ andthereafter releasing at 23° C. Hardness 23° C. (Shore 00) 55  22 45 45Water tightness 23° C. × 24 hours ◯ ◯ X X (during 50% compression)Foamability Continuous or independent ◯ ◯ X X High-Tg acrylate A:IBA-100 (produced by Soken Chemical & Engineering Co., Ltd.; Mw: 10,000,Tg before ultraviolet curing: 20° C.) High-Tg acrylate B: Beamset 101(produced by Arakawa Chemical Industries, Ltd.; Mw: 430, Tg beforeultraviolet curing: 18° C.) Low-Tg acrylate C: Shikoh-UV-3000B (producedby Nippon Synthetic Chemical Industry Co., Ltd.; Mw: 18,000, Tg afterultraviolet curing: −52° C.) Low-Tg acrylate D: Shikoh-UV-3700B(produced by Nippon Synthetic Chemical Industry Co., Ltd.; Mw: 38,000,Tg after ultraviolet curing: −59° C.) Low-Tg acrylate E: Shikoh-UV-2000B(produced by Nippon Synthetic Chemical Industry Co., Ltd.; Mw: 13,000,Tg after ultraviolet curing: −40° C.) Cationic-polymerizable compound F:Epicoat 828 (produced by Japan Epoxy Resin Co., Ltd., Mw: 380)Cationic-polymerizable compound G: PB-3600 (produced by Daicel ChemicalIndustries, Ltd.) Radical polymerization initiator: Irgacure 184(produced by Ciba Speciality Chemicals Co., Ltd., 1-hydroxycyclohexylphenyl ketone) Cationic polymerization initiator: Cyracure CPI-6992 (TheDow Chemical Company: sulfonium salt) Tackifier resin: terpene phenoltype resin, softening point: 120° C. Thermoplastic elastomer: VylonGA-6400 (produced by Toyobo Co., Ltd.: saturated polyester resin)

Next, as condition 2, each of the above sealing materials of Examples 1to 7 was hot-melted, foamed and discharged under the followingcondition, and then each evaluation was carried out. The results areshown in Table 3.

(Condition 2):

Each of the above sealing materials of Examples 1 to 7 was hot-melted ata temperature of 120° C. with Foam Melt Applicator (trade name “FM-151”,produced by Nordson Corporation), and then nitrogen gas was mixed intothe melting-conditioned sealing material at a gas cylinder pressure of0.005 MPa, and then the melting-conditioned sealing material containingthe pressurized nitrogen gas was discharged into the air at adischarging pressure of 2.0 MPa and thereby foamed.

TABLE 3 (Condition 2) Example 1 Example 2 Example 3 Example 4 Example 5Example 6 Example 7 Ultraviolet-curable High-Tg acrylate A 25 40 10 5component High-Tg acrylate B 25 40 Low-Tg acrylate C 50 50 50 50 55 50Low-Tg acrylate D 25 10 25 10 25 20 Low-Tg acrylate E 100Cationic-polymerizable 10 compound F Cationic-polymerizable 10 compoundG Ultraviolet polymerization Radical polymerization 3 3 3 3 3 3 3initiator initiator Cationic polymerization 1 initiator Tackifier resin5 Thermoplastic elastomer 5 Foam density densities 3 3 3 3 3 3 3 Flowing◯ ◯ ◯ ◯ ◯ ◯ ◯ Irradiation intensity: 2000 mW/cm² Sticky or not No No NoNo No No No Irradiation time: 30 seconds Heat-resistant blocking 100°C./after 5 days Δ Δ Δ Δ Δ Δ Δ Compression-set 80° C. × 24 hours (50% ◯ ◯◯ ◯ ◯ ◯ ◯ compression) and thereafter releasing at 23° C. Hardness 23°C. (Shore 00) 45 45 45 46 48 50 55 Water tightness 23° C. × 24 hours Δ ΔΔ Δ Δ Δ Δ (during 50% compression) Foamability Continuous or independentΔ Δ Δ Δ Δ Δ Δ High-Tg acrylate A: IBA-100 (produced by Soken Chemical &Engineering Co., Ltd.; Mw: 10,000, Tg before ultraviolet curing: 20° C.)High-Tg acrylate B: Beamset 101 (produced by Arakawa ChemicalIndustries, Ltd.; Mw: 430, Tg before ultraviolet curing: 18° C.) Low-Tgacrylate C: Shikoh-UV-3000B (produced by Nippon Synthetic ChemicalIndustry Co., Ltd.; Mw: 18,000, Tg after ultraviolet curing: −52° C.)Low-Tg acrylate D: Shikoh-UV-3700B (produced by Nippon SyntheticChemical Industry Co., Ltd.; Mw: 38,000, Tg after ultraviolet curing:−59° C.) Low-Tg acrylate E: Shikoh-UV-2000B (produced by NipponSynthetic Chemical Industry Co., Ltd.; Mw: 13,000, Tg after ultravioletcuring: −40° C.) Cationic-polymerizable compound F: Epicoat 828(produced by Japan Epoxy Resin Co., Ltd., Mw: 380)Cationic-polymerizable compound G: PB-3600 (produced by Daicel ChemicalIndustries, Ltd.) Radical polymerization initiator: Irgacure 184(produced by Ciba Speciality Chemicals Co., Ltd., 1-hydroxycyclohexylphenyl ketone) Cationic polymerization initiator: Cyracure CPI-6992 (TheDow Chemical Company: sulfonium salt) Tackifier resin: terpene phenoltype resin, softening point: 120° C. Thermoplastic elastomer: VylonGA-6400 (produced by Toyobo Co., Ltd.: saturated polyester resin)

In the above Tables 2 and 3, the evaluations of the foam density, theflowing, the UV reactivity, the heat-resistant blocking, thecompression-set, the hardness, the water tightness and the foamabilityare specifically as follows.

<Foam Density>:

While being foamed under each condition above, the sealing material wasapplied onto mold-releasing paper into the shape of a bead of about 2 cmin width and about 15 cm in length, thus preparing a test piece.

After the test piece had cooled and solidified, its mass was measured.The test piece was immersed into a measuring cylinder of 250 mlcontaining 200 ml of water to measure the volume of the test piece.Assuming that the specific gravity of the test piece was 1.0, the foamdensity was calculated by the following equation.

Foam density=volume of test piece/mass of test piece

Incidentally, in the case of the two-package type sealing material, theabove test was carried out after the foaming-curing.

<Flowing>:

While being foamed under each condition above, the sealing material wasapplied onto the surface of a stainless steel sheet “SUS-304” as definedin JIS G4305 at a foam density of 3 so as to be 5 mm in bead width and 4mm in height, thus obtaining a sealing foam.

Thereafter, the sealing foam was left under 23° C./50 to 60 RH for 5minutes, and thereafter the bead width was measured to make evaluationby the following marking.

mark “◯”: the width of 5 mm is maintained.

mark “X”: the bead width has exceeded 5 mm.

<UV Reactivity>:

While being foamed under each condition above, the sealing material wasapplied onto the surface of a stainless steel sheet “SUS-304” at a foamdensity of 3 so as to be 3 mm in bead width and 4 mm in height, thusobtaining a sealing foam.

The aforementioned sealing foam was subjected to UV curing at anirradiation intensity of 2,000 mW/cm² for an irradiation time of 30seconds. Thereafter, the cured sealing foam was left under an atmosphereof 120° C. to evaluate the surface stickiness by the following marking.

mark “◯”: the stickiness of the surface is not recognized.

mark “X”: the stickiness of the surface is recognized.

<Heat-Resistant Blocking>:

The ultraviolet-cured sealing foam as obtained under the same conditionsas those for the above UV reactivity test was compressed to a positionof 2 mm (50% compression) with a stainless steel sheet “SUS-304” andfixed with a clip. This was left in a hot-air-circulating oven of 100°C. for 5 days, and then the condition of the adhesion to the “SUS-304”was checked to make evaluation by the following marking.

mark “◯”: the adhesion to the “SUS-304” is not recognized.

mark “Δ”: there is not complete adhesion to the “SUS-304”, but adhesionprint is recognized.

mark “X”: the adhesion to the “SUS-304” is recognized.

<Compression-Set>:

The ultraviolet-cured sealing foam as obtained under the same conditionsas those for the above UV reactivity test was compressed to a positionof 2 mm (50% compression) with a stainless steel sheet “SUS-304” andfixed with a clip. While this 50% compressed condition was kept, thefoam was left under a temperature of 80° C. for 24 hours. Thereafter,the compression was released under 23° C./50 to 60% RH. After the foamhad been left under 23° C./50 to 60% RH for 24 hours, the thickness ofthe test foam of which the compression had been removed was measured.The compression-set ratio was calculated by the following equation andevaluated by the following marking.

Compression-set ratio=(a1/a0)×100

-   -   a0: Thickness (mm) of test foam before test    -   a1: Thickness (mm) of test foam after test

Mark “◯”: the compression-set ratio is not less than 80%.

Mark “X”: the compression-set ratio is less than 80%.

<Hardness>:

The ultraviolet-cured sealing foam as obtained under the same conditionsas those for the above UV reactivity test was measured for the Shorehardness 00 with “GS-754G” produced by Teclock Co., Ltd. The largernumerical value means the more hardness.

<Water Tightness>:

The ultraviolet-cured sealing foam as obtained under the same conditionsas those for the above UV reactivity test was compressed to a positionof 2 mm (50% compression) with a stainless steel sheet “SUS-304” anddeformed into the U-shape in this condition. Water was added to ameasuring line. The foam was left under 23° C./50 to 60% RH for 24 hoursto check whether water bled out of the convex part of the U-shape, andit was evaluated by the following marking.

mark “◯”: there is no water bleeding.

mark “Δ”: water bleeding was seen a little.

mark “X”: water bleeding was seen.

<Foamability>:

The ultraviolet-cured sealing foam as obtained under the same conditionsas those for the above UV reactivity test was checked as to its foamedcondition with a video microscope by the following marking.

mark “◯”: independent cells are formed in the inside of the foam.

mark “Δ”: independent cells and continuous cells coexist in the insideof the foam.

mark “x”: no independent cell is seen in the inside of the foam, butcontinuous cells are formed.

[Synthetic Evaluation of Performance]:

From the results as shown in Tables 1 and 2, it is understood that thesealing materials of Examples 1 to 7 have excellent heat resistance,excellent compression-set, high softness (Shore hardness of about 45 toabout 50), and high water tightness, and further a foamed conditionwhere independent cells are formed.

On the other hand, as to the sealing material of Comparative Example 1,since the mixing amount of the thermoplastic elastomer which is notultraviolet-curable exceeds 5 weight % based on the total amount of theresin components, the heat resistance is low.

As to the sealing materials of Comparative Examples 2 and 3, since theydo not contain any thermoplastic elastomer which is notultraviolet-curable, they have enough heat resistance. However, theyhave too low melt-viscosity at 120° C. to sufficiently prevent theflowing and also have low water tightness and further fail to ensureindependent cells.

The results as shown in Table 3 are results of evaluations underconditions deviating from the favorable conditions such as gas cylinderpressure of 0.01 to 0.1 MPa and discharging pressure of 2.7 to 9.7 MPa.Therefore, when compared with the results as shown in Table 2 satisfyingthe aforementioned favorable conditions, even if the sealing materialsare the same, the evaluation of the foamability is a little degraded,and accompanying this, the evaluations of the heat resistance and thewater tightness are also a little degraded. However, the aforementionedgas cylinder pressure and discharging pressure are no other thanfavorable conditions for applying the sealing material, and whencompared with the results as shown as to Comparative Examples 1 to 3 inTable 2, the superiority is high.

INDUSTRIAL APPLICATION

The sealing material and the method of foaming application thereof,according to the present invention, for example, can favorably used as asealing material and method of foaming application thereof for such ashousehold appliance parts, automobile interior and exterior parts, andautomobile door modules, and for between metal sheets.

1. A sealing material, which comprises an ultraviolet-curable component and an ultraviolet polymerization initiator, wherein in cases where the sealing material further comprises a thermoplastic elastomer which is not ultraviolet-curable, its content is not higher than 5 weight % based on the total amount of resin components, and wherein the sealing material comprises an acrylate as the ultraviolet-curable component in a ratio of not less than 50 weight % based on the total amount of the resin components wherein the acrylate has a weight-average molecular weight of 500 to 50,000 and has a glass transition temperature of −70 to 0° C. after ultraviolet curing, and wherein the sealing material has a melt-viscosity at 120° C. of 1,000 to 50,000 mPa·s.
 2. A sealing material according to claim 1, which further comprises an acrylate having a glass transition temperature of not lower than 10° C. before ultraviolet curing as another ultraviolet-curable component.
 3. A method of foaming application of a sealing material, which comprises the steps of: hot-melting the sealing material as recited in claim 1; mixing a pressurized inert gas into the melted sealing material; discharging the melted sealing material containing the pressurized inert gas into the air to thus foam the sealing material and simultaneously apply it to a place necessary to seal, thus making a sealing foam; and irradiating this sealing foam with ultraviolet rays, thus curing the sealing material; wherein: the mixing of the inert gas is carried out by: using nitrogen gas as the inert gas; pressurizing the nitrogen gas into a pressure of 0.01 to 0.1 MPa; and blowing the pressurized nitrogen gas into the sealing material; and the applying of the sealing material is carried out at a discharging pressure of 2.7 to 9.7 MPa.
 4. A method of foaming application of a sealing material according to claim 3, wherein the sealing foam has a foam density of 2 to
 5. 5. A method of foaming application of a sealing material, which comprises the steps of: hot-melting the sealing material as recited in claim 2; mixing a pressurized inert gas into the melted sealing material; discharging the melted sealing material containing the pressurized inert gas into the air to thus foam the sealing material and simultaneously apply it to a place necessary to seal, thus making a sealing foam; and irradiating this sealing foam with ultraviolet rays, thus curing the sealing material; wherein: the mixing of the inert gas is carried out by: using nitrogen gas as the inert gas; pressurizing the nitrogen gas into a pressure of 0.01 to 0.1 MPa; and blowing the pressurized nitrogen gas into the sealing material; and the applying of the sealing material is carried out at a discharging pressure of 2.7 to 9.7 MPa.
 6. A method of foaming application of a sealing material according to claim 5, wherein the sealing foam has a foam density of 2 to
 5. 